Specific Aims: The zebrafish genome is being sequenced by the Sanger Center, and Drs. Zon and Zhou are participating in the consortium to achieve a high quality assembly of the zebrafish genome sequence by 2006. We propose to comparatively evaluate gene expression patterns, profiles, and function during hematopoiesis in several vertebrate systems, improving our understanding of blood diseases such as anemias and leukemias. 1. Establish and compare gene expression patterns in vertebrate models by using in situ hybridization and microarray assays. 2. Apply bioinformatics tools to find gene regulation networks in animal disease models and human patient samples. 3. Map mutant genes and develop a reverse genetic strategy for zebrafish.